This invention relates to high volume low pressure or HVLP paint spray guns having a paint cup and utilizing a syphon tube to draw the paint from the paint cup and deliver it to the gun. In such guns it has been desirable to provide a passage for air to enter the paint cup to prevent the creation of a vacuum which would resist or prevent paint from being drawn up the suction tube. Such an air passage, if unprotected, can easily be clogged with paint, particularly when the gun is used to paint horizontal surfaces. This need has led to a number of designs for check valves and other structures for paint cup spray guns, all of which attempt to both permit air to enter the paint cup and prevent paint from exiting the paint cup at that point. Conventional check valves and other designs attempting to address this problem have been costly, complicated, difficult to clean and often have imperfect operation.
The present invention overcomes deficiencies of the prior art by providing a simple, low cost and easily cleanable check valve which both admits air to the paint cup to prevent creation of a vacuum and prevents egress of paint or other liquid from the paint cup through the air venting path.